This invention relates to wellhead tools, particularly to a wellhead bowl protector and retrieving tool for preventing damage to loading and sealing areas in the upper bowl of the wellhead during drilling or workover operations.
A wear bushing or bowl protector is typically positioned in the wellhead immediately below the blowout preventers for the purpose of protecting and preventing damage to the interior of the wellhead during workover or drilling operations. The wear bushing is usually positioned in the wellhead as a new bit or milling tool is run into the wellbore for drilling new or additional hole. In a typical installation, the wear bushing is positioned about the drill string tubing on top of the last stabilizer incorporated in the drill string and lowered into position. The wear bushing is positioned in the wellhead and rests on an internal circumferential shoulder formed in the wellhead. Once the wear bushing is in position, it will take the abusive rotating action of the drill pipe and protect the interior of the wellhead from damage during the drilling operations. Also, the wear bushing protects the interior of the wellhead during addition or pulling, i.e., "tripping", of the pipe in or out of the wellbore.
Periodically during the drilling operation, tripping of the pipe is required for replacement of the drill bit which has been worn-out or dulled to the point that the penetration rate is not acceptable. Also, the drill string may be pulled for conducting various downhole tests which may be required during the drilling operation. During the course of drilling or working over a well, the wear bushing may be positioned in and retrieved from the wellhead several times. Retrieval of the wear bushing from the wellhead generally occurs as the drill string is pulled from the well. Typically the wear bushing rides out of the hole on top of the top most stabilizer in the drill string.
Bowl protectors and retrieving tools are currently available and have been in use for a number of years. The typical retrieving tool is equipped with an affixed or stationary lug or lugs that slide into a J-slot formed in the bowl protector. Once in position, the retrieving tool is rotated slightly so that the protruding lug is retained in the J-slot for carrying the bowl protector out of the wellhead. While this system of removing a bowl protector is workable, it has serious drawbacks. For example, it is difficult to judge the engagement of the lugs on the retrieving tool within the J-slot in the bowl protector, particularly when a substantial length and weight of the drill string is suspended in the wellbore below the retrieving tool. Protruding lugs have often sheared off of retrieving tools employed in this method of removing the well bushing because the lugs were not properly aligned in the J-slot formed in the bowl protector and could not support the weight of the drill string suspended on the retrieving tool. Valuable rig time and expense is thus incurred while another retrieving tool or other means is utilized to remove the bowl protector from the wellbore.
Many wells are drilled on federal leases. Governmental regulations require that frequent wellbore tests be conducted during the drilling process. For example, federal regulations require that blowout preventers be tested at least once a week. In order to test the blowout preventers, the wellhead bowl protector must be removed to permit placement of a test plug in the wellhead immediately below the blowout preventers. To conduct the test, the drilling operator must trip out of the wellbore, thereby removing the bowl protector so that he may conduct the test of the blowout preventers. Tripping out of the well, and consequently tripping back in, may be acceptable for a relatively shallow well, however it is a very expensive use of drill rig time for deeper wells. In such a situation, the drilling operator partially pulls the drill string out of the well and then utilizes a retrieving tool to remove the bowl protector from the wellhead. The apparatus of the present disclosure is particularly suited for reliably and efficiently removing the bowl protector from the wellhead while suspending several thousand feet of drill pipe below the retrieving tool.
It is therefore an object of this invention to provide a wear bushing and retrieving tool which cooperate to remove the wear bushing from the wellhead without the risk of shearing engagement lugs off of the retrieving tool.
It is another object of the invention to provide a wear bushing and retrieving tool including spring actuated lugs received in a circumferential slot formed in the wear bushing for engagement with and removal of the wear bushing from the wellhead.